No. You didn't get pregnant in October.
Early ultrasounds can be pretty accurate, almost to the day. By the end of the pregnancy there is a margin for error of many days. When the doctor gave you the due date of August 20, how far along did he say you were (i.e., 6 weeks, 7 weeks, etc.)? If the ultrasound was early, like at least in your first trimester, it is reliable enough to indicate that you conceived in late November. I can't see it being your ex from October 14 in any case, that would be way too early even if the ultrasound was off by two weeks.
Thank you annie!!! the earliest ultra sound i received gave me a due date of august 14 my new doctor moved it to august 20 due to the size of baby and that was mid feb does that help?>
Your earliest ultrasound was at what point in the pregnancy, i.e., what week (like, 10 weeks 3 days or whatever)?
It was jan 29 just ending my 1st trimester
If you had a 12th-week ultrasound, it will be reliable to within a few days, maybe +/- 6 days if that much. Your estimated ovulation date would be around November 21, with a conception window (because of the margin for error) of the 16th or so through the 25th of November. We are definitely not talking about anything in October. I can't help you further than that because you didn't say when you had sex in November, but it is clear that the sex in October did not produce the pregnancy.